Method and apparatus for controlling the diameter of spiral pipe



March 10, 1970 HUTTQN 3,499,307

I METHOD AND APPARATUS FOR CONTROLLING THE DIAMETER OF SPIRAL PIPE Filed March 14. 1968 l NVENTO R/S HUTTON,

y A'noms United States Patent 3,499,307 METHOD AND APPARATUS FOR CONTROLLING THE DIAMETER OF SPIRAL PIPE Andrew H. Hutton, Middletown, Ohio, assignor to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Filed Mar. 14, 1968, Ser. No. 713,164 Int. Cl. B21f 3/02 U.S. Cl. 72-135 Claims ABSTRACT OF THE DISCLOSURE A method for fixing and maintaining constant the diameter of free-formed spiral pipe as it is being formed from a strip of metal, which comprises the step of helically disposing a flexible, endless member of sufficient length to provide one complete spiral wraparound around the first width of metal strip which forms the first helical convolution of said pipe.

An apparatus for fixing and maintaining constant the diameter of free-formed spiral pipe as it is being formed from a strip of metal, which comprises a flexible, endless member of sufficient length to provide one complete spiral wraparound, in uniform contact with said pipe, around the first width of metal strip which forms the first helical convolution of said pipe.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method and apparatus for free-forming spiral pipe from a strip of metal and in particular to a method and apparatus for fixing and maintaining constant the diameter of the pipe as it is being formed.

Description of the prior art One conventional way of making spiral pipe is disclosed by U.S. Letters Patent No. 1,939,581, in the name of William Tesmer. There a mandrel, which must be changed for each diameter of pipe desired, is provided around which a girdle or flexible member drives and forms a strip of metal into successive helical convolutions so as to form a spiral pipe. The apparatus of Tesmer has proven to be undesirable because a complete and expensive set of mandrels is required covering the large range of pipe diameters desired, and because the combination of a forming girdle in conjunction with a mandrel is cumbersome and time consuming When it is desired to change the mandrel so that a spiral pipe of a different diameter may be produced.

A further way of making spiral pipe is disclosed by U.S. Letters Patent No. 3,256,724, in the name of A. D. Wiley, which teaches a method and apparatus for free-forming spiral pipe without the cumbersome use of a mandrel and a forming girdle. Briefly, Wiley provides a three roll bending apparatus comprising a heel roll, a buttress roll and a knee roll. The heel and buttress rolls are disposed beneath the strip of metal and the knee roll is disposed above the strip of metal and causes the strip to curl upwardly as it is forced therethrough.

Wiley attempts to generally fix and maintain a constant diameter of free-formed spiral pipe as it is being formed from a strip of metal by the three roll bending apparatus by utilizing a chain carrying a plurality of rollers, one roller between each link in the chain. The chain is anchored at both ends, one end to the heel roll and the other end to the buttress roll, and embraces the first convolution of the strip along its outside edge, the rollers contacting the strip convolution.

While the free-forming bending apparatus of Wiley has ICC proven to be generally satisfactory, it has certain definite limitations. This is true, for example, with respect to the manner in which Wiley attempts to fix and maintain a constant diameter of free-formed spiral pipe as it is being formed. Some of the problems which have been encountered include:

(1) Wiley does not disclose an effective and efficient method for quickly changing to the production of spiral pipe of varying diameters while at the same time accurately controlling the diameter of the pipe which is produced,

(2) The flexible chain of Wiley marks the spiral pipe being formed, requiring use of rollers between each link of the chain. The rollers do not provide for uniform contact between the chain and the spiral pipe.

(3) The Wiley chain and roller system tends to push the formed spiral pipe back toward the forming end.

(4). The rollers between each link of the Wiley chain require the chain to be above the spiral pipe which is being formed. Accordingly, the Wiley chain is longer than the desired helix and thus reforms the spiral pipe and causes a somewhat improper helix angle.

SUMMARY OF THE INVENTION The present invention comprises a method and apparatus for fixing and maintaining a constant diameter of free-formed spiral pipe as it is being formed from a longitudinal strip of metal. Briefly, the method comprises the step of helically disposing a flexible, endless member of sufficient length to provide one complete spiral wraparound around the first width of metal strip which forms the first helical convolution of the pipe, and the apparatus comprises a flexible, endless member of sufficient length to provide one complete spiral wraparound, in uniform contact with the pipe, around the first width of metal strip which forms the first helical convolution of the pipe.

The apparatus of the present invention also utilizes a serving system of sheaves into which the flexible, endless member is threaded. The system of sheaves provides directional control and continuous circulation of the flexible, endless member as successive helical convolutions are formed from the metal strip. Additionally, the apparatus of this invention may also include size indicating means associated with the flexible, endless member to indicate changes in the diameter of the spiral pipe which is being formed.

The system of this invention alleviates the myriad problems present in prior art devices. For example, the flexible, endless member of the present invention is most attractive due to its simplicity as compared to the prior art devices. Further, the flexible, endless member of this invention accurately fixes and maintains a constant diameter of free formed spiral pipe as it is being formed from a strip of metal, while at the same time it is relatively easy to adapt the member to accommodate spiral pipe of varying diameters. The flexible, endless member of I this invention provides uniform contact with the spiral pipe and does not push the spiral pipe back toward the forming end thereof. Finally, the flexible, endless member of this invention provides uniform contact against the spiral pipe and thus produces a more accurate helix angle.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a diagrammatic plan view with a portion of the incoming strip shown in cross-section showing the flexible, endless member diameter control system according to the present invention.

FIGURE 1a is a schematic representation of the size indicating means when it comprises a separate cable attached to a variable transformer and a volt meter is associated with the transformer.

FIGURE lb is a schematic representation of the size indicating means when it comprises a separate cable attached to a load cell.

FIGURE 2 is a cross-sectional view taken on the line 22 of FIGURE 1.

FIGURE 3 is a cross-sectional view taken on the line 33 of FIGURE 1.

FIGURE 4a is a fragmentary cross-sectional view taken on the line 4a-4a of FIGURE 1, showing a lock seam for helically corrugated spiral pipe.

FIGURE 4b is a fragmentary cross-sectional view similar to FIGURE 4a, showing a but weld for helically corrugated spiral pipe.

FIGURE 40 is a fragmentary cross-sectional view similar to FIGURE 4a, showing a lap joint for helically corrugated spiral pipe.

FIGURE 4d is a fragmentary cross-sectional view similar to =FIGUR-E 4a, showing a lap joint for helically corrugated spiral pipe which is designed to prevent diam- .eter growth.

FIGURE 5 is a perspective view of the means for changing the diameter of the loop around the pipe.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The three roll bending apparatus diagrammatically shown in the drawing is exemplary of prior art devices for free-forming spiral pipe from metal strip. Briefly, this bending apparatus comprises the heel roll 10, the buttress roll 11 and the knee roll 12. The rolls and 11 are disposed beneath the strip and the roll 12 above the strip to cause the strip to curl upwardly.

The three roll bending apparatus may be utilized to receive either flat strips or corrugated strips. By way of illustration, corrugated strip has been shown. However, it should be clearly understood that cylindrical rollers may be substituted for the members 10, 11 and 12 so that the apparatus will receive a fiat strip. In operation, the corrugated strip 14 is being fed by means, not a part of this invention, into the three roll bending apparatus. The angular disposition of the members 10, 11 and 12 and the rollers 10a, 11a and 12a positioned thereon determines the diameter of the pipe which it is desired to make. As the spiral pipe is formed, the edge 14a is disposed adjacent the edge 14b. The edges 14a and 14b are then subsequently brought either into abutting relationship or overlapping relationship depending upon the type of joint it is desired to produce. In order to fix and maintain constant the diameter of the pipe being produced, irrespective of the diameter chosen, the present invention provides a flexible, endless member 16 of sufficient length to provide one complete spiral wraparound 16a around the first width of metal strip which forms along the outer edge of the first helical convolution 18a of the spiral pipe 18. As can be seen, the spiral wraparound 16a provides substantially uniform contact with the spiral pipe 18.

At this point, it should be emphasized that while corrugated strip has been shown by way of illustration, the flexible, endless member v16 of this invention may be used for free forming smooth wall, spiral pipe as well as for free forming helically corrugated spiral pipe, such as lock seam, but welded or lap joint helically corrugated spiral pipe, shown in FIGURES 4a, 4b, 4c and 4d. It should also be pointed out that the flexible, endless member 16 may comprise either an endless cable, belt or chain. While it has been found that a flexible, endless belt or chain is the preferred restraint when smooth wall, spiral pipe is free formed, and that a flexible endless cable is the preferred restraint when helically corrugated, spiral pipe is free formed, such embodiments are only exemplary, because it would be quite obvious, for example, that the flexible, endless member could comprise a flexible, endless chain when corrugated spiral pipe is free formed.

The flexible, endless member 16 is threaded into a 4 serving system of sheaves, indicated by the numerals 20- '83, to provide directional control and continuous circulation of the cable as the rolls 10, 11 and 12 form the spiral pipe 18 from the strip 14. The arrows 42 indicate the direction of circulation of the endless cable 16 as the spiral pipe 18 is formed. Since the spiral wraparound 16a of the flexible, endless member 16 must remain motionless with respect to the free formed spiral pipe 18, the member 16 must flow in the direction in which the strip 14 travels. Additionally, since the flexible, endless ,member 16 moves with the surface of the free formed pipe 18 at the same speed at which the pipe spins, there is no relative motion between the endless member 1'6 and the pipe 18, and thus there is no slipping or sliding of the pipe 18 within the spiral wraparound 16a of the endless member 16. This latter fact is important because the absence of friction prevents abrasion.

The flexible, endless member 16 will function satisfactorily in maintaining constant the diameter of free formed, helically corrugated spiral pipe if the spiral wrap around 16a is warpped around any corrugation in the first width of metal strip 14 which forms the first convolution 18a of the spiral pipe 18. However, it has been found preferable that, if a nonwelded seam is formed, such as, for example, the lock seam of FIGURE 4a or the lap joint of FIGURES 4c and 4d, the endless cable should be positioned in a groove near the seam as this is a location of greater rigidity. With respect to butt welded seams, as shown in FIGURE 4b, it is believed that a balanced condition is preferable and that this condition is optimally obtained when the spiral wrap around 16a is located around the corrugation in the center of the first width of metal strip 14 which forms the first convolution 18a of the spiral pipe 18.

As can be seen from FIGURES 13, the incoming flexible, endless member 16 passes through the grooves 10b and 11b in the rollers 10a and 11a of the heel roll 10 and the buttress roll 11, respectively, and engages the metal strip 14 at the heel roll 10, slightly before the invert centerline, indicated by the arrow 18b.

The flexible, endless member 16 of the present invention is capable of being adjusted to augment the production of any desired diameter of spiral pipe. Ascan be seen, the sheave 20 is rotatably mounted upon a carriage 44 which may be selectively positioned upon the frame member 46. When it is desired to produce a larger diameter pipe, the carriage 44 may be moved forward by removing the bolts 44a and selectively positioning the carriage elsewhere on the frame 46 and replacing the bolts 44a. The receiving holes 44b for the bolts 44a may be positioned at any desired distance between centers, but it has been found that 6 inch increments are preferable. After the carriage 44 has been selectively positioned upon the frame 46, the sheave 20 may be selectively positioned upon the carriage 44 by means of the threaded shaft 48.

It has been found that best results are obtained in fixing and maintaing constant the diameter of free formed corrugated spiral pipe when the flexible, endless member 16 is selected so that the center of the cable lies substantially at or below the neutral axis of the corrugated surface of the pipe. For example, a 5 inch diameter cable is used for 2 /3 inch x /2 inch corrugated 16 guage strip.

It has also been found that the present invention is enhandced by providing size indicating means 50 associated with the endless cable 16 to indicate variations in the diameter of the spiral pipe 18 being formed. The size indicating means may comprise a separate cable attached to a variable transformer, as shown in FIG. 1a. The variable transformer is in turn connected to a volt meter. The size indicating means may also comprise a separate cable attached to a load cell, as shown inFIG. lb, or simply a metal measuring strap wrapped around the pipe 18. If a strap is utilized, a scale of deviation may be marked thereon which is based either upon changes in pipe circumference or directly upon diviations in pipe diameter.

While certain preferred embodiments of the invention have been specifically illustrated and described,'it is understood that the invention is not limited thereto, as many variations will be apparent to those skilled in the art, and the invention is to be given its broadest interpretation within the terms of the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a method of free forming helically corrugated spiral pipe comprising the steps of moving a longitudinally corrugated strip of metal longitudinally through a bender disposed at an angle of more than 90 to the centerline of said spiral strip to impart to said strip a helical configuration, and maintaining constant the diameter of the formed pipe by maintaining constant the length of the helix formed during the first helical convolution, the improvement which comprises the steps of maintaining constant the length of the helix formed during the first helical convolution by selecting a flexible, endless member of suflicient length to at least provide one complete spiral wrap around said pipe and having a diameter so that the center of said member will be substantially at or below the neutral axis of the corrugated surface of said pipe, helically disposing said flexible, endless member around the first width of metal strip which forms the first helical convolution of said pipe, said spiral wrap being in uniform contact with said pipe, and moving said flexible, endless member with said pipe so that said spiral wrap around and said pipe are substantially free from relative motion.

2. The method of claim 1, wherein said flexible, endless member is disposed in the first groove of the corrugations along the outside edge of the first helical convolution of said pipe.

3. The method of claim 1, wherein the outer edge of each convolution which is formed is juxtaposed to the inside edge of the incoming strip.

4. The method of claim 1, wherein the outer edge of each convolution which is formed is in overlapping relation with the inside edge of the incoming strip.

5. The method of claim 1, wherein the outer edge of each convolution which is formed is in interlocking relation with the inside edge of the incoming strip.

6. A method for fixing and maintaining constant the diameter of free formed helically corrugated spiral pipe as it is being formed from a strip of metal, which comprises the steps of selecting a flexible, endless member of suflicient length to at least provide one complete spiral Wrap around around said pipe and having a diameter so that the center of said member will be substantially at or below the neutral axis of the corrugated surface of said pipe, helically disposing said flexible, endless member around the first width of metal strip which forms the first helical convolution of said pipe, and moving said flexible endless member with said pipe so that said spiral wrap around and said pipe are substantially free from relative rotation.

7. In an apparatus for free forming helically corrugated spiral pipe from a strip of longitudinally corrugated metal, comprising a bender disposed at an angle of more than to the centerline of said strip and through which said strip of metal is fed longitudinally, said bender imparting to said strip a helical configuration, and means to fix and maintain the diameter of the formed pipe, the improvement wherein said means to fix and maintain the diameter of the formed pipe comprises a flexible, end less member of suflicient length to provide at least one complete spiral wrap around, in uniform contact with said pipe, around the first width of metal strip which forms the first helical convolution of said pipe, the center of said flexible member lying substantially at or below the neutral axis of the corrugated surface of said pipe.

8. The apparatus according to claim 7, wherein said flexible, endless member is threaded into a serving system of sheaves to provide directional control and continuous circulation of said member as said bender imparts helical convolutions to said strip of metal.

9. The apparatus according to claim 8, wherein size indicating means is associated with said flexible endless member to indicate variations in the diameter of said pipe being formed by said bender.

10. The apparatus according to claim 9, wherein said size indicating means comprises a separate cable attached to a variable transformer and a volt meter associated with said transformer.

11. The apparatus according to claim 9, wherein said size indicating means comprises a separate cable attached to a load cell.

12. The apparatus according to claim 8, wherein said flexible, endless member is a cable.

13. The apparatus according to claim 8, wherein said flexible, endless member is a chain.

14. The apparatus according to claim 8, wherein said flexible, endless member is a belt.

15. An apparatus for fixing and maintaining constant the diameter of free formed helically corrugated spiral pipe as it is being formed from a strip of longitudinally corrugated metal, which comprises a flexible, endless member of sufficient length to provide one complete spiral wrap around, in uniform contact with said pipe and lying substantially at or below the neutral axis of the corrugated surface thereof, around the first width of metal strip which forms the first helical convolution of said pipe.

References Cited UNITED STATES PATENTS 1,939,581 12/1933 Tesmer 72-l45 3,256,724 6/1966 Wiley 72l36 3,393,546 7/1968 Fay 72138 MILTON S. MEHR, Primary Examiner US. Cl. X.R. 

